Single Point Perspective

I've been learning a lot about how Renaissance artists 'invented' single point perspective today.  This wee exercise explains the convergence of octhogonals and vanishing points.  It is also, I realize the only  photo I took today so apologies that it is rather lame. 

In the evening A and I caught up woth some of her old work colleagues which she hadn't seen for 20 plus years - very pleasant evening.